In Japanese Kokai No. 7 6146-497 and in Ann. Rep. Sankyo Res. Lab. 29, 75-98 (1977) there are described a number of 4H-pyrido[1,2-a]pyrimidin-4-one derivatives, bearing in the 3-position an aminoalkyl substituent, wherein the amino group may be part of a morpholino-, a piperidino- or a piperazine moiety, which compounds are taught to be useful as cardiovascular agents and as agents acting on the central nervous system.
In the European Patent application having the publication No. 37,265 there are described a number of 3-(1-piperidinylalkyl)-4H-pyrido[1,2-a]pyrimidin-4-one derivatives wherein the piperidine ring is substituted with an aroyl radical or a functional derivative thereof, which compounds are potent serotonin-antagonists.
The compounds of the present invention differ from the prior art compounds by the substitution of the 4H-pyrido[1,2-a]pyrimidin-4-one group by a 5H-thiazolo[3,2-a]-pyrimidin-5-one, a 5H-1,3,4-thiadiazolo[3,2-a]pyrimidin-5-one or a 3,4-dihydro-2H,6H-pyrimido[2,1-b][1,3]thiazin-6-one group and by their useful properties in the treatment of psychotropic diseases.